1. Field of the Invention
This invention relates to the field of dual stage actuator (DSA) type suspensions for disk drives including hard disk drives. More particularly, this invention relates to the field of electrical connections to microactuators in a hard disk drive suspension, particularly to piezoelectric microactuators.
2. Description of Related Art
Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. FIG. 1 is an oblique view of an exemplary prior art hard disk drive and suspension for which the present invention is applicable. The prior art disk drive unit 100 includes a spinning magnetic disk 101 containing a pattern of magnetic ones and zeroes on it that constitutes the data stored on the disk drive. The magnetic disk is driven by a drive motor (not shown). Disk drive unit 100 further includes a disk drive suspension 105 to which a magnetic head slider (not shown) is mounted proximate a distal end of load beam 107. Suspension 105 is coupled to an actuator arm 103, which in turn is coupled to a voice coil motor 112 that moves the suspension 105 arcuately in order to position the head slider over the correct data track on data disk 101. The head slider is carried on a gimbal which allows the slider to pitch and roll so that it follows the proper data track on the disk, allowing for such variations as vibrations of the disk, inertial events such as bumping, and irregularities in the disk's surface.
Both single stage actuated disk drive suspensions and dual stage actuated (DSA) suspension are known. In a single stage actuated suspension, only voice coil motor 112 moves suspension 105.
In a DSA suspension, as for example in U.S. Pat. No. 7,459,835 issued to Mei et al. as well as many others, in addition to voice coil motor 112 which moves the entire suspension, at least one microactuator is located on the suspension in order to effect fine movements of the magnetic head slider to keep it properly aligned over the data track on the spinning disk.
In a DSA suspension, the microactuator(s) provide much finer control and much higher bandwidth of the servo control loop than does the voice coil motor alone, which effects relatively coarse movements of the suspension and hence the magnetic head slider. DSA suspensions carry the disadvantages, however, of higher piece count and greater assembly costs. The most expensive additional part used in DSA suspensions is the microactuator itself, which is typically a flat piece of piezoelectric crystal, typically lead zirconate titanate (PZT), and its associated manufacturing challenges. The negative side, or the V− or ground terminal, of the PZT microactuator is typically adhered onto the suspension using conductive epoxy. The stainless steel surface of the suspension base plate or other stainless steel part typically provides the ground contact for the PZT. The positive side, or the V+ terminal, of the PZT is often connected to a wire or other conductor carrying a driving voltage by conductive epoxy. Such a connection can be time consuming to make and/or requires special bonding equipment. Additionally, the use of conductive epoxy from the PZT positive electrode to the PZT driving voltage conductor can introduce potentially contaminating epoxy particles into the disk drive assembly process, and presents additional manufacturing complications. The bonding process also increases process time, and it can be difficult to maintain manufacturing consistency.
Soldered connections have also been used, typically to provide the driving voltage connection from the V+ electrode of the PZT to a flexible electrical conductor such as a short length of wire. The wire and its connection to the PZT is sometimes referred to as a tail weave. Tail weaves are typically constructed using exacting and hence expensive skilled labor.
FIG. 2 is a top plan view of suspension 105 of FIG. 1, which is a representative prior art DSA suspension, and FIG. 3 is a close-up view thereof in the area around microactuators 114. Two PZT microactuators 114 are affixed to suspension 105 on microactuator mounting shelves 118 that are formed within base plate 103, such that PZTs 114 span respective gaps in base plate 103. PZT Microactuators 114 expand and contract thereby effecting fine movements of load beam 107 and the magnetic head slider mounted at the distal end of the load beam. Microactuators 114 are firmly held within the cavity on mounting shelves 118 by non-conductive epoxy 116 at each end of the microactuators 114. The positive and negative electrical connections can be made from the PZTs to the suspension's flexible wiring trace and/or to the grounded base plate by a variety of techniques including those disclosed in commonly owned U.S. Pat. No. 7,751,153 to Kulangara et al. especially FIG. 7B, U.S. Patent Publication No. 2010/0177445 by Fuchino, and U.S. Patent Publication No. US 2009/0086379 by Hanya et al. An exemplary electrical connection to the positive terminal or face 122 of PZT 114 can be seen in FIG. 3. The negative (ground) electrical connection is usually made from the negative terminal or face of PZT 114 to baseplate 103 using conductive epoxy (not shown). The PZTs can be located in various locations within the suspension including on cavities within baseplate 105, on the load beam 107, or at or near the head gimbal assembly which is located at the distal end of load beam 107. Many variations have been proposed and/or implemented.